As has already been pointed out, you have to install an ARM-capable chroot on your device and install all the required packages in that chroot. However, doing so in your home directory wastes a lot of valuable space. Instead, it can be done on your SD-card using a computer running on an appropriate Linux OS (tested on Linux Mint 17 and Ubuntu Trusty). As I did not find any information about this anywhere else, I put it here as an answer to an old question.
The following instructions assume you want to install a debian jessie chroot in the directory jessie.
Creating and populating the image file on a desktop computer
Creating an empty image file
To create an 1GB image called IMAGE.img in the current working directory, do:
dd if=/dev/zero of=IMAGE.img bs=1G count=1
Note that the B in GB is left out. "if" stands for "input file", "of" for
"output file" and "bs" for "block size".
There are more efficient commands out there, but those only work on certain
types of file systems, as far as I know. This one also works on an SD-card or
a tempfs. Please note the use of /dev/zero and not /dev/random or /dev/urandom
as that would take a lot longer and make it take a lot longer to transfer the
image between devices later on.
Creating a file system on the image
Without the file system, the phone would not be able to store any data on the
image. Without a file system, you cannot yet mount the image to a directory,
only to a block-device.
This bash-command will output the next empty loop device into the variable LOOP:
$LOOP=$(sudo losetup -f)
Next, assign the image to a block device:
sudo losetup $LOOP IMAGE.img
Next, create the ext4 file system on it:
sudo mkfs -t ext4 $LOOP
Next, detach the image from the loop device:
sudo losetup -d $LOOP
If you get command not found errors, just install the missing programmes.
Mount the image file on the computer to access it
Now, create a temporary directory in the working directory:
mkdir jessie
and mount the image file IMAGE.img to it:
sudo mount -o loop IMAGE.img $(pwd)/jessie
The command pwd will make sure you give mount an absolute path to your
current working directory.
Populating the image with the new operating system with qemu-debootstrap
The next step will be to use qemu-debootstrap to download the necessary files.
This is easy if qemu-debootstrap is available as is the case on Ubuntu and
derived OSes. If you get command not found errors when executing
qemu-debootstrap --help, try to install the appropriate package, which can be
done on Ubuntu via:
sudo apt-get install qemu-user-static
To download all required files and ready the new OS, run the following command:
sudo qemu-debootstrap --arch=armhf jessie ./jessie http://http.debian.net/debian
Please note that the first jessie stands for the OS version whereas the
second jessie stands for the directory where the files are to be installed.Now you can unmount the image as the rest of the work has to be done on the
phone. Do so via:
sudo umount $(pwd)/jessie
If you cannot install qemu-debootstrap, see the next section.
Populating the image with the new operating system without qemu-debootstrap
Please skip this section if you have qemu-debootstrap available. You will still
need a native debootstrap for you architecture, though. If this happens to be
armhf, just use the above command line but replace qemu-debootstrap by
debootstrap. If not, follow this section.
To download all required files for the new OS, run the following command:
sudo debootstrap --arch=armhf --foreign jessie ./jessie \
http://http.debian.net/debian
Now you can unmount the image as the rest of the work has to be done on the
phone. Do so via:
sudo umount $(pwd)/jessie
Transfer image to the phone
Now best create a tar archive from this which you then copy to your
phone. It does not matter whether the archive is put on the SD-card or
the internal storage. Create the archive on the desktop using:
tar -cvzf jessie.tar.gz IMAGE.img
Now, on your phone, turn on ssh support to copy the image over. You might also
do that using a USB-cable instead. Since the ssh server is reset on every
reboot, start the ssh service on the phone via:
sudo service ssh start
Next, copy the image via:
scp jessie.tar.gz phablet@ubuntu-phablet:$COPYDIR
where the variable COPYDIR contains the directory where the image shall be
stored. This command assumes that your username on the phone is phablet and
the phone's hostname is ubuntu-phablet. You can find out both by issuing echo $USER
and echo $HOSTNAME on the phone, respectively.
Now you only have to extract the archive wherever you want the image to reside. Assume the directory where you want the image to be located
is stored in the variable IMAGEDIR. Extract the image there via the bash
command:
( cd $IMAGEDIR; tar -xvzf $COPYDIR/jessie.tar.gz; )
You might now remove the archive:
rm $COPYDIR/jessie.tar.gz
Finalizing and using the image on the phone
If you did not turn on the ssh server on the phone, do so now via:
sudo service ssh start
Next, mount your image to a directory of your choice (in this case "jessie"):
sudo mount -o loop $IMAGEDIR/IMAGE.img $(pwd)/jessie
Now, enter your chroot for the first time via:
ssh localhost "sudo chroot $(pwd)/jessie /bin/bash"
If you had qemu-debootstrap available on your computer, you're all done. Use
the above 2 commands to connect to your chroot. If not, you still have to
execute the following command once you are inside your chroot, in order to
properly setup the OS:
/debootstrap/debootstrap --second-stage
Summary of how to access the chroot
If you followed the above steps, you should be able to access your chroot using
this simple script on the phone:
#!/bin/bash
sudo service ssh start
ssh localhost "sudo chroot jessie /bin/bash"
You have to first ssh into your own phone from the phone due to apparmor restrictions of the terminal app. The terminal app is only allowed to execute binaries in certain locations and neither your home directory nor the SD card are among those. The ssh service, however, does not have such restrictions.
